Clustering Email Appliance

Question

Hi, 
 I am having a Sophos email appliance ES100 in our environment and would like to purchase or configure another appliance to built a cluster for redundancy. Before going forward, Could anyone please clarify. 
 What will be best solution to built a cluster to mitigate the scenario, if one appliance goes down the other should able to take over? 
 Can we have to built a sophos cluster with one physical and one virtual appliance? 
 What about the license, if we go for a physical appliance or a virtual appliance? 
 How the cluster will work in sophos? 
 
 It would be great if anyone clarify on the above points. Thanks in advance. 
 
 Regards 
 Ansar

Neil_Evolve · Accepted Answer

Hi Ansar, 
 You can find all the information you require in the ESA documentation; http://esa.sophos.com/ug/pdf/sea_ug.pdf , chapter 5.3.6. 
 You can cluster physical and virtual appliances, but they must be running the same software versions. 
 Remember, clustering does not provide load-balancing, failover or failback, these functions would need to be provided by third-party SMTP load-balancers or DNS round-robin.

lferrara · Answer

Ansar, 
 I did a cluster 2 weeks ago between 2 ES1100. Just start the new appliance (virtual or physical same model and same OS version), activate the appliance, give it a new name, new ip address and let it to update all the definitions, then at the reboot connect to it and join the cluster (ip of the existing ESA node). Once you have done the cluster, create proper MX records on DNS zone (both external and internal) and make sure to redirect traffic to the new ESA ip address by internal mail server and any MTA relay. Take note that creating a new public MX record requires up to 24 hours. 
 Regards